The described subject matter relates generally to gas turbine engines, and more specifically to cases and frames for gas turbine engines.
Gas turbine engines operate according to a continuous-flow, Brayton cycle. A compressor section pressurizes an ambient air stream, fuel is added and the mixture is burned in a central combustor section. The combustion products expand through a turbine section where bladed rotors convert thermal energy from the combustion products into mechanical energy for rotating one or more centrally mounted shafts. The shafts, in turn, drive the forward compressor section, thus continuing the cycle. Gas turbine engines are compact and powerful power plants, making them suitable for powering aircraft, heavy equipment, ships and electrical power generators. In power generating applications, the combustion products can also drive a separate power turbine attached to an electrical generator.
Gas turbine engines are supported by frames which typically include one or more struts. The struts connect outer and inner cases and cross a flow passage carrying working gases such as combustion products. Due to the need for the struts to retain their strength at high temperatures, frames used on the turbine side of the engine have been produced using investment cast superalloys. However, casting of superalloys becomes more difficult and expensive as the radial dimension of the frame increases. As such, a need has been recognized for reducing the temperature of the frame without sacrificing the efficiency gains seen with higher combustion temperatures.